This invention relates to material screening apparatus. More particularly, it relates to a variably tilting trommel screening apparatus.
Screens are utilized for sorting material by size in various industries including construction, waste disposal, landscaping, and building demolition. Some such screens are substantially planar and screen by oscillating or shaking. Alternately, trommel screens are cylindrical in shape, open at both ends, and rotate. Conventional trommel screens are operated tilted at an angle from horizontal. The material to be processed is dumped into the higher end and the rotation causes the material to tumble toward the lower end with some of the material falling down through the screen and the balance discharged out the lower end. The trommel screens typically have an axial length of two or more diameters and are thus quite bulky in size and must be transported lengthwise on trailers. Trommel screens are typically configured to require an input conveyor, an exit conveyor for material that has passed all the way through the trommel and an additional conveyor to convey screened material out from under the trommel. The size and necessary ancillary equipment require an involved process in setting up the apparatus and make these trommels inconvenient or impractical for many applications. A further disadvantage is that material processed in conventional trommel screens has a limited retention time within the trommel. This has two undesirable effects: First, the material to be processed may circulate through the entire axial length of the trommel without being fully processed. That is, material that should have fallen through the screen does not and is dumped out the discharge end of the screen. Secondly, the limited retention time allows only a very limited effect of breaking up the material that is being processed. Additionally, conventional trommel screens open at both ends and have minimal or no flexibility for varying the rotation speed and tilt angle.